Atomizers have hitherto been used to administer drugs into the lungs of artificially respirated patients by means of correspondingly generated aerosols, which are added to the inhaled air. The administration is usually performed by inserting a pneumatic atomizer into the inspiration tube leading from the respirator to the patient connection, the so-called Y-piece. The breathing gas flowing through the atomizer during the inhalation phase is enriched with aerosol, and the breathing gas is also mixed with the propellant gas of the atomizer due to the pneumatic drive of the atomizer. Special measures must therefore be taken to guarantee the desired oxygen concentration for the patient. A prior-art ultrasonic atomizer inserted at the same point is free from this drawback. Nevertheless, it is disadvantageous that the aerosol is generated at a point relatively remote from the patient. Part of the drug aerosol precipitates in the tube system on its way to the patient connection; more losses occur, especially in the case of continuous atomization without interruption, e.g., due to the propellant gas flow, which flows unused into the exhalation line, or due to the increased precipitation because of lack of removal of the aerosol.
The loss due to the escape of unused gas-aerosol mixture reaches up to 90%, and sometimes even more, especially in modes of operation needed in pediatric and especially neonatological applications. The distortion of the oxygen concentration due to the propellant gas flow is also unacceptable in this field of application. The arrangement of prior-art drug atomizers near the patient between the Y-piece and the tube connector is also impossible because of the additional dead space volume, which may be several times the tidal volume in the case of pediatric and neonatological applications. In addition, the exhaled gas would also be enriched with aerosol in such a case, or the atomizer would have to be synchronized with the breathing cycle in a complicated manner.
DE 43 00 880 C2 describes an arrangement, which is to solve these problems by an ultrasonic atomizer located directly before the tube in the Y-piece being supplied, synchronously with the breathing, with a small amount of the substance to be atomized during the inhalation via a nozzle, and by this substance being atomized by the atomizer directly into the tube.
The drawback of this arrangement is, on the one hand, that triggering and a tidal volume-dependent metering of the amount of liquid is necessary, and, on the other hand, that no aerosol selection is performed. The latter means that droplets of all sizes formed flow to the patient. This results in the deposition of considerable amounts in the tube and in the upper part of the respiratory tract because of excessively large droplets. In addition, complete atomization of the amount of liquid injected onto the atomizer is not guaranteed, so that so much excess will gradually collect in the course of a plurality of breathing cycles that the atomization will come to a standstill. As an inherent feature of the system, the temperature of the atomizer surface will increase, as a result of which sensitive, protein-containing substances will be destroyed.